1. Field of the Invention
The present invention relates to a method of fabricating an LCD panel, and more particularly, to a method of combining a first substrate and a second substrate of an LCD panel.
2. Description of the Prior Art
The advantages of liquid crystal displays include better portability, lower power consumption, and lower radiation. Therefore, LCDs are widely used in various portable products, such as notebooks, personal digital assistants (PDA), electronic toys, etc. A conventional LCD panel comprises a first substrate, a second substrate, and a liquid crystal layer filled up between the first and the second substrate. In the conventional method of implanting the liquid crystal layer, the first substrate and the second substrate are adhered together, and then the combined substrates are placed in a vacuum chamber so that the liquid crystal is implanted between the substrates by capillarity. However, the traditional method of implanting liquid crystal layer requires too much time, and causes the uniformity and yield problems as the large-size LCD develops. Therefore a one drop filling (ODF) method is highly developed to resolve the above-mentioned problems so that LCD panels can be applied in large-sized monitors.
Please refer to FIG. 1 to FIG. 3. FIG. 1 to FIG. 3 are schematic diagrams of fabricating an LCD panel according to the prior art. As shown in FIG. 1, according to the method of fabricating an LCD panel of the prior art, a substrate 10 having a specific size such as a glass substrate or a plastic substrate is provided, and a plurality of display panel 14 patterns are defined in an actually used area 12 for manufacturing display components of the second substrate. The second substrate can be a TFT substrate comprising thin film transistors, pixel electrodes, scan lines (gate line), and data lines (signal line) arranged in an array. Further the second substrate can be a color filter on array (COA) substrate or an array on color filter (AOC) substrate having thin film transistors, pixel electrodes, scan lines, and data lines arranged in an array and a color filter therein. If the second substrate is a COA substrate, the color filter is located above the thin film transistors; if the second substrate is an AOC substrate, the color filter is located below the thin film transistors. The substrate 10 has an orientation layer with orientation patterns thereon, and a plurality of spacers installed on the surface of the orientation layer. A sealant 16 is applied to a frame area outside the actually used area 12 of the substrate 10. Then liquid crystal molecules are dropped on the surface of the substrate 10 with pressure, motors, or others similar ways of applying the theorem of injector or ink jet. Following that, the substrate 10 and a first substrate such as a glass substrate or a plastic substrate comprising necessary components are positioned in a vacuum chamber where proper mechanical force and pressure are applied to affix the substrates. While the second substrate is an ordinary TFT substrate, the first substrate is a color filter substrate; while the second substrate is a COA or an AOC substrate, however, the first substrate is a glass or a plastic substrate. A gap for liquid crystal molecules is retained by spacers installed between the substrates. Finally the combined substrates are properly segmented and tested by external circuit.
For further explaining problems that may happen during the affixing process according to the prior art, FIG. 2 and FIG. 3 only show portions of the first and the second substrate. As shown in FIG. 2, while using ODF method to fabricate LCD panels according to the prior art, a first substrate 26 and a second substrate 28 are positioned respectively on a surface of an upper stage 22 and a lower stage 24 in a vacuum chamber 20. The first substrate 26 comprises display components such as color filters, black matrix, transparent electrodes, and orientation patterns, etc.; the second substrate 28 comprises display components such as thin film transistors, pixel electrodes, scan lines, data lines, orientation patterns, a plurality of liquid crystal drops 34 and spacers 36 arranged in an array, and a sealant 30 applied to a frame area on the surface. The power that the upper and lower stages use to carry the first and second substrates is vacuum adsorbability, mechanical force, friction, or ESD sucking disc. The orientation pattern on the surface of the first substrate 26 corresponds to the orientation pattern on the surface of the second substrate 28 for orienting liquid crystal molecules.
Following that, the vacuum chamber 20 is vacuumed, and a gap d1 is kept between the first substrate 26 and the second substrate 28 to horizontally align the first substrate 26 and the second substrate 28. After the alignment process as shown in FIG. 3, a mechanical force is applied to the upper stage 22 with a driving device 38 to vertically lower the first substrate 26 until it contacts the sealant 30 on the surface of the second substrate 28, and makes sure the frame areas on the first substrate 26 and the second substrate 28 tightly affixed together. Then the vacuum chamber 20 is returned to atmospheric pressure so that liquid crystal drops can spread out between the first substrate 26 and the second substrate 28 and forms a uniform liquid crystal layer. Finally, the first substrate 26 and the second substrate 28 are exited from the vacuum chamber 20, and a curing process is performed to harden the sealant 30 by using UV exposure apparatus and/or heater, or by other hardening methods.
For affixing the frame areas on the first and the second substrates, the mechanical force is equally applied to the upper stage for lowering the first substrate according to the prior art. During the affixing process, however, defects may occur because of particles or glass chippings remaining on the surface of the upper and lower stages. These gap defects (gap mura) could make the gap between substrates collapse, and further crush the spacers.